How to dry herbs

A glut of basil in August, a rosemary bush that needs cutting back, a thyme plant still going in October: the question is the same every year. Learning how to dry herbs is how a summer garden keeps seasoning winter cooking, and the method matters more than most people expect. Dry them too slowly and they mold. Dry them too hot and the flavor that made them worth growing disappears with the steam. This guide follows how to dry herbs the way university extension services teach it: harvest at the right stage, match the method to the herb, and store the result whole and airtight so it still smells like the plant a year later.

When to harvest herbs for drying

Timing is the first decision in how to dry herbs, and extension services agree on it with unusual consistency. Harvest herbs based on their stage of growth rather than a specific date, as Iowa State Extension puts it: most herbs have the best flavor and fragrance when harvested just as flower buds appear but before they open, when volatile oil levels are highest. Penn State Extension says the same in slightly different words: most herbs are best for drying just before the flowers first open, and flowering herbs tend to taste somewhat bitter. Nebraska Extension adds the reason: stems in the bud stage, not yet flowered, are when leaves contain the highest amount of aromatic, essential oils.

The time of day matters too. Harvest in the early morning after the dew has dried and before temperatures rise, per Iowa State Extension, or on a sunny day in mid-morning after the dew has evaporated, per Penn State Extension. Either way, the leaves should be dry when you cut them; wet leaves take longer to dry and are more likely to mold. Get this stage right and the rest of how to dry herbs gets easier, because leaves cut at peak oil need less time and less heat to finish.

How much to cut, and when to stop

How much to take depends on the plant. For leafy annual herbs, Iowa State Extension advises cutting plants back to within 4 to 6 inches of the ground, making cuts just above a leaf or pair of leaves to encourage regrowth. Penn State Extension likewise says to cut stems just above a leaf or pair of leaves, and to leave 4 to 6 inches of stem for later growth. Perennial herbs should be harvested more lightly: Iowa State Extension says to remove no more than about one-third of the top growth at a time, or only the leafy tips on some species. Nebraska Extension gives a seasonal cutoff for perennials such as thyme and sage: stop harvesting stems by mid-September, so the plants can keep growing and store enough energy for overwintering.

Two exceptions are worth knowing before you cut. Herbs grown for seed, such as dill or coriander, should not be cut back at all; Iowa State Extension says to let them mature and harvest the seed heads as they turn brown. And if your plants are already blooming, Nebraska Extension says to cut the blooming stems back about six inches, let new growth develop, and harvest that new growth once it is at least six inches long. Our how to start seeds indoors guide covers starting the next round of herbs from seed, and our herb growing guides cover individual herbs such as basil and thyme.

How to prepare herbs for drying

Whatever method you choose for how to dry herbs, the herbs should be fresh and clean when you start. Iowa State Extension says to wash the stems in cold running water and then drain them thoroughly on paper towels. Penn State Extension gives the same sequence with one more detail: rinse in cool water, gently shake off excess moisture, and pat dry with a paper towel, or use a salad spinner to remove as much moisture as possible. Nebraska Extension is more sparing: if the leaves and stems are not clean, brush off loose dirt with a soft pastry brush, and wash only if the herbs are very gritty, patting off excess water before drying begins.

Then sort ruthlessly. Penn State Extension says to remove any bruised, soiled, or imperfect leaves and stems, and to inspect plants, especially seeds, for insects. Only dry non-bruised and unsoiled leaves and stems. A damaged leaf in a bundle is a damp spot in a bundle, and damp spots are where mold starts. Work on clean countertops with clean utensils, wash your hands, and start with herbs that are free of pesticides if they are destined for the kitchen, as Nebraska Extension notes.

How to dry herbs by air-drying

Air-drying is the simplest method for how to dry herbs, and the one extension services describe first. It costs nothing, needs no equipment, and suits the herbs that dry readily. It is also the slowest method, so it suits dry air and herbs that are not too tender.

Bundles

Tie 5 to 8 stems into small bundles and hang them in a dark, warm location at 70 to 80°F, per Iowa State Extension, which gives 2 to 4 weeks for drying depending on temperature and humidity. Nebraska Extension describes the same setup — small, loose bunches hung upside down from a rack, line, or cord — and warns against making the bunches too large, because leaves will not dry properly and mold may develop if enough air cannot circulate through the bunch. The ideal place, Nebraska Extension says, is a warm, dark, and well-ventilated place at about 90°F, and the kitchen is a poor choice despite looking attractive, because kitchens are often full of condensation from cooking.

Penn State Extension adds two practical details for bundles. If you tie with a rubber band, it will tighten as the stems dry so stems will not fall out of the cluster. And to keep dust off the herbs, cover them with a paper bag punched with holes: the holes allow air to circulate, and for seedy herbs the bag catches falling seeds. Hang bundles away from the sink, stove, or dishwasher, where there is a lot of moisture.

Trays

Tray drying works well for short-stemmed herbs or individual leaves, per Iowa State Extension: spread herbs in a single layer on screens or drying trays and place them in a warm, dark location with good air circulation until fully dry. Penn State Extension gives the same method for small-leaved herbs — lay them on a fine stainless steel or food-safe plastic screen or on paper towels — and for larger leaves, remove them from the stems and lay them on screens or paper towels without allowing the leaves to touch. Up to five layers of herbs and paper towels can be dried this way, changing the paper towels as they absorb moisture.

How to dry herbs in a dehydrator

A dehydrator is the best compromise in how to dry herbs: faster than air-drying, gentler than an oven, and the right answer for tender herbs that would mold in a bundle. Penn State Extension says herbs can be dried in a dehydrator if the temperature can be set between 95 and 110°F, placing stems on the trays so they do not touch, and drying larger leaves separately. Do not dry herbs with fruits or vegetables, because the flavors may mix and the moisture contents are different.

Nebraska Extension gives a slightly wider range, 95 to 115°F, and a useful time expectation: drying times vary from 1 to 4 hours, and you should check the herbs periodically. Place stems in a single layer on the trays. Either way, the principle is the same as air-drying — heat, low humidity, and air movement, which Penn State Extension names as the three things successful drying needs — delivered in hours instead of weeks.

How to dry herbs in the microwave

Microwaving is the fastest way to dry a small batch, and the one that needs the most attention. Penn State Extension says parsley, basil, and celery leaves dry well in some microwave ovens, but warns that an oven with a wattage rating of 1,000 or higher may heat too fast for this method, and to read the manufacturer's directions first. Arrange washed and dried herbs one layer thick between microwave-safe paper towels, microwave on high for 2 to 3 minutes per cup, starting with 1 minute and mixing after every 30 seconds, checking for dryness as you go. The caution is blunt: watch carefully, because if there is not adequate volume, the paper towels can catch fire.

Iowa State Extension gives a similar procedure: place clean herbs on a paper plate or towel and heat on high for 1 to 3 minutes, turning stems or stirring leaves every 30 seconds. Nebraska Extension uses smaller intervals: place small bunches between two paper towels, microwave for about 1 minute, then continue at 20 to 30 second intervals, turning the herbs each time, and never leave the microwave unattended because herbs can scorch and start burning. Test for dryness by crushing a few leaves: they should be dry and brittle, crumbling into leaf bits when rubbed between your hands.

How to dry herbs in the oven, and why it is the last choice

Oven drying works, but extension services rank it last among the heat methods in how to dry herbs, and the reason is flavor. Penn State Extension says oven drying is generally not recommended because even the lowest temperature destroys much of the flavor, oils, and color of the herbs. Nebraska Extension agrees: it is not advisable to dry herbs in the oven, because no matter how low the temperature is, the flavor degrades more than with other methods. Iowa State Extension adds the same warning in general terms: while faster than air drying, excessive heat can reduce flavor, color, and essential oils.

If an oven is what you have, keep it as cool as possible. Penn State Extension says to set the oven at the lowest temperature, not above 180°F, for 3 to 4 hours with the oven door open, and notes that the oven light in some ovens may provide enough heat to dry herbs on its own. Iowa State Extension gives the same ceiling: heat at no more than 180°F for 3 to 4 hours with the oven door slightly open. Nebraska Extension offers a narrower use for the oven: final drying of leaves that still show moisture, spread on a cookie sheet at 110°F or less. Sun drying, for completeness, is not recommended by Penn State Extension, because high humidity prevents the quick removal of moisture — in a humid climate, the leaves lose color and flavor before they dry.

Drying herb seeds

Seeds follow a different rhythm in how to dry herbs, because the goal is a mature, dry seed rather than a pliable leaf. Penn State Extension says the seeds of dill, caraway, mustard, and fennel can be left on the plant until mature, then cut the flower stalks or pull the entire plant, hang it upside down, and shake the seeds out when dry. Examine the seeds for insects, rub off the husks between your hands, and blow away the chaff. Iowa State Extension gives the same maturity signal for seed herbs: harvest seed heads as they turn brown, and dry the seeds thoroughly after collection. If you are saving seed for planting rather than for the kitchen, skip the heat treatment described below — Penn State Extension warns that the heat method is not suitable for seeds you want for planting.

How to tell herbs are dry, and the insect treatment

However you dry them, herbs are not ready until they are completely dry. Penn State Extension says herbs are sufficiently dry when leaves are crispy and crumble easily between the fingers, and warns that complete dryness is what prevents mold growth during storage. Nebraska Extension gives the same test in the microwave section and it applies everywhere: leaves should be dry and brittle, crumbling into leaf bits or powder when rubbed between your hands. If they bend instead of crumbling, they need more time.

Air-dried herbs and seeds need one more step that heat-dried herbs do not. Penn State Extension says they need treatment to destroy any insects or insect eggs: heat them at 160°F for 30 minutes, or freeze them at 0°F or lower for at least 48 hours. The heat method will reduce flavor, so for herbs you care about most, freezing is the gentler choice — and for seed you intend to plant, freezing is the only choice of the two.

How to store dried herbs

Storage is where dried herbs either keep their flavor or quietly lose it, and the rules are consistent across sources. After herbs are completely dry, Iowa State Extension says to store them in airtight jars in a cool, dry location, and to keep containers away from light and heat, which reduce herb quality. Penn State Extension says the same: store in airtight, vapor-proof containers in a cool, dry, dark place such as a cupboard or drawer, away from stoves and sinks, and do not set them near the stove top or on a windowsill. Nebraska Extension adds that dried herbs should be kept out of direct sunlight to prevent their color from fading. That cool, dark, airtight routine is the storage half of how to dry herbs.

Store whole, label, and check

Store them whole. Penn State Extension says storing herbs whole is preferred because the herb holds its oil and retains its flavor longer, and Nebraska Extension says flavor will be best if the leaves are stored whole and crushed just before adding them to food. If stems were dried whole, Iowa State Extension says to remove and crush or crumble the leaves before storing — but that advice sits alongside the same keep-whole principle: crush only as much as you need, when you need it, and leave the rest whole in the jar.

Label every jar with the herb name and the harvest date, as Nebraska Extension advises, and examine the jars daily at first to check whether any moisture has condensed on the inside of the glass. If it has, take the contents out and spread them for further drying. Most dried herbs keep well for up to a year, per Penn State Extension — judge their strength by aroma, and replace a jar that smells like dust rather than the herb. Dried herbs can also be stored in the refrigerator or freezer in freezer jars or heavy-duty aluminum foil to avoid odor transfer, per Penn State Extension, but be careful when moving a container from cold storage to a warm kitchen: condensation may form, and the herbs may absorb enough moisture to spoil.

How to use dried herbs: the fresh-to-dried conversion

The last step in how to dry herbs is knowing how much of the result to use. Dried herbs are 3 to 4 times stronger than fresh herbs, per Penn State Extension, so the general rule of thumb is to use about one-quarter to one-third as much dried herb as fresh. The exact conversion is:

That table comes straight from Penn State Extension, which gives the same conversion in both of its herb-drying guides. One more substitution from the same source: 2 to 3 teaspoons of dill seed or dill weed provides the flavor of one head of fresh dill. Start at the low end of the range when you are cooking with a herb for the first time — you can add more dried herb to a dish, but you cannot take it back out.

Which herbs dry best which way

Not every herb suits every method, and choosing wrong is the most common reason a batch disappoints in how to dry herbs. Penn State Extension draws the key line: less tender herbs such as sage, thyme, and winter savory are the easiest to air-dry in small bundles, while tender-leaf herbs such as basil, tarragon, lemon balm, and the mints have a high moisture content and will mold if not dried quickly. The table below follows that line, using the extension methods above:

Herbs grown in containers follow the same rules, and our potting soil calculator sizes the mix if you are potting up a new round of herbs, while our how much potting soil a container needs guide works out how many bags that takes.

What not to do

A few mistakes undo an otherwise good batch in how to dry herbs, and extension sources name them plainly:

• Do not dry wet or damaged herbs. Only dry non-bruised and unsoiled leaves and stems, per Penn State Extension. Damaged material molds first and can spoil a whole bundle.
• Do not make big, tight bundles. Nebraska Extension warns that bunches that are too large will not dry properly and mold may develop if air cannot circulate. Small and loose beats big and impressive.
• Do not dry tender herbs slowly. Basil, tarragon, lemon balm, and the mints mold if not dried quickly, per Penn State Extension. Give them a dehydrator, a microwave, or a tray — not a bundle in a still room.
• Do not reach for the oven first. Penn State Extension and Nebraska Extension both say oven heat degrades flavor more than other methods. Use the oven only as a last resort, at or below 180°F with the door open.

Storage mistakes to avoid

• Do not store herbs before they are completely dry. Leaves must be crispy and crumble easily, per Penn State Extension. A jar sealed while leaves still bend is a jar that will mold.
• Do not store dried herbs by the stove or on the windowsill. Heat and light reduce quality, per Iowa State Extension, and Penn State Extension names both spots specifically as places not to store herbs.
• Do not sun-dry in a humid climate. Penn State Extension says high humidity prevents the quick removal of moisture, and the herbs lose color and flavor while they wait.

How to dry herbs, done well, is mostly patience plus one decision: the right method for the herb in your hand. Harvest just before flowering, dry small batches with plenty of air, test for crispness before you jar anything, and store the jars whole, airtight, and in the dark. Do that, and the thyme you cut this autumn will still taste like thyme next autumn.

Sources

• Penn State Extension — Preserving Herbs by Drying (dried-to-fresh strength and conversion, harvest timing, drying methods, storage up to one year)
• Penn State Extension — Let's Preserve: Drying Herbs (harvest stage and stem length, tender vs. less tender herbs, air-drying, microwave, dehydrator and oven details, dryness test, insect treatment, storage)
• Nebraska Extension in Lancaster County — Harvesting & Drying Herbs (bud-stage harvest, mid-September perennial cutoff, bundle size and drying place, dehydrator time, labeling and condensation checks)
• Iowa State University Extension and Outreach — Growing, Harvesting, and Drying Herbs (growth-stage harvest, annual and perennial cutting rules, air-drying time and temperature, silica sand note, oven ceiling, storage)